Method of hydraulically controlling a marine speed reducing and reversing machine in crash astern operation

ABSTRACT

In carrying out a crash-go-astern operation for switching operating means ( 2   a ) of a hydraulic clutch mechanism ( 100 ) provided to a marine reduction and reverse gear ( 1 ) from a forward setting (F) to a reverse setting in a stroke so as to abruptly stop in traveling ahead, a propeller speed (PN) is detected in neutral (N) halfway through the switching and initial fitting pressure (Po) of a reverse driving clutch ( 90 ) is calculated by using a map of the initial fitting pressure (Po) of reverse clutch pressure (Pr) formed according to the propeller speed based on a ship load (SL) in advance before switching to the reverse setting (R), the reverse driving clutch ( 90 ) is set at the calculated initial fitting pressure (Po) when the operating means is switched to the reverse setting (R), and then the reverse clutch pressure (Pr) is increased to a maximum value (Pm) as an engine speed (EN) increases.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is the United States National Phase under 35 U.S.C. § 371 ofInternational Application No. PCT/JP/00/06006 filed Sept. 4, 2000, whichclaims priority to Japanese Patent Application Nos. JP 11-248599, filedSept. 2, 1999 and JP 2000-75217, filed Mar. 17, 2000, the disclosures ofwhich are herein incorporated by reference in their entireties.

TECHNICAL FIELD

The present invention relates to a hydraulic control method of a marinereduction and reverse gear in a crash-go-astern operation for switchinga clutch in the marine reduction and reverse gear from a forward setstate to a reverse set state so as swiftly stop a ship traveling ahead.

BACKGROUND ART

In order to swiftly stop a traveling ship and to switch the ship fromtraveling ahead to traveling astern in some cases, an operation called acrash-go-astern operation for instantaneously switching a clutch of amarine reduction and reverse gear from a forward set state to a reverseset state (to be more precise, the clutch goes through a neutral stateinstantaneously at one time between the forward set state and thereverse set state) is carried out conventionally. In other words, byswitching the clutch to one for reverse driving, a reverse driving forceis applied to a propeller which is rotating forward to brake. However,because a load is suddenly applied to an engine when the clutch isswitched from the intermediate neutral state to the reverse set state,there is a fear of stalling. Therefore, in prior-art control, athreshold value for avoiding stalling is asset for each degree of a setengine speed during execution of the crash-go-astern operation, theclutch which has been switched to the reverse set state is returned tothe neutral state if an actual engine speed is lower than the thresholdvalue, and the clutch is switched to the reverse set state after theactual engine speed increases to some degree. In another case, a certainthreshold value with regard to an engine load is set, a state of theengine load is detected, the clutch is similarly returned to the neutralstate if the engine load is over the threshold value when the crutch isswitched to the reverse setting to show a state of an overload with afear of stalling, and the clutch is returned to the reverse settingafter the state of the engine load gets out of the overload state.

In these methods, however, the clutch is switched again to the neutralstate if the actual engine speed exceeds the threshold value again orthe engine shows the overload state again after the clutch has beenreturned to the reverse set state. When the clutch is in the neutralstate, external forces other than water do not act on the ship, i.e., abraking force is not applied. Because engagement and disengagement ofthe clutch are repeated until the actual engine speed increasessufficiently or until the engine gets out of the overload state asdescribed above, considerable time is required for stopping the ship andan essential purpose of the crash-go-astern operation, i.e., an abruptstop of the ship cannot be achieved satisfactorily.

SUMMARY OF THE INVENTION

In the present invention, as a hydraulic clutch control method of amarine reduction and reverse gear in a crash-go-astern operation forswitching operating means of a hydraulic clutch mechanism provided tothe marine reduction and reverse gear from a forward setting to areverse setting in a stroke so as to abruptly stop a ship travelingahead, fitting pressure of a reverse driving clutch is maintained for awhile at standby clutch pressure set between a minimum value and amaximum value and appropriate for avoiding stalling if it is judged thatthere is a fear of the stalling due to a shock of clutch switching inthe operation and the fitting pressure of the reverse driving clutch isincreased if it is judged that there is no fear of the stalling.

As described above, because the clutch is not brought into the neutralstate completely but the reverse driving clutch is fitted at the standbyclutch pressure in avoiding the stalling, the reverse driving force dueto the clutch fitting is applied to the propeller which is rotatingforward as a braking force and time required for stopping the ship canbe shortened.

As timing of hydraulic control of the reverse driving clutch andjudgement of stalling, in the first policy, the fitting pressure of thereverse driving clutch is first increased to the maximum value as atarget when the operating means of the hydraulic clutch mechanism isswitched to the reverse setting in the crash-go-astern operation and thefitting pressure is reduced to the standby clutch pressure if it isjudged that there is the fear of the stalling in a process of increasingof the fitting pressure.

A threshold value of an engine speed is set as a criterion of judgementof a state in which there is the fear of the stalling and a detectedengine speed and the threshold value are compared with each other.

It is also possible that a threshold value of a load applied to anengine is set and a detected degree of a load applied to the engine andthe threshold value are compared with each other.

It is also possible that an engine speed and a ship velocity aredetected.

It is also possible that the standby clutch pressure is increased andreduced repeatedly at or below the maximum value of the clutch fittingpressure as an upper limit to apply the braking force to the propellerin stages or to eliminate the load applied to the engine in stages.

The increase in the fitting pressure of the reverse driving clutch basedon a judgement of a state in which there is no fear of the stalling maybe carried out according to an increase in an engine speed or areduction in an engine load. As described above, by automaticallycontrolling to increase working hydraulic pressure of the reversedriving clutch, it is possible to save time and effort for a valveswitching operation and to fit the reverse driving clutch in an optimumpressure increasing pattern to effectively apply the reverse drivingforce as the braking force to the propeller.

In the invention, in the crash-go-astern operation for switchingoperating means of a hydraulic clutch mechanism provided to the marinereduction and reverse gear from a forward setting to a reverse settingin a stroke so as to abruptly stop in traveling ahead, initial fittingpressure of a reverse driving clutch is calculated from certaincriterion of judgement of a ship in advance before the switching to thereverse setting and the reverse driving clutch is set at the calculatedinitial fitting pressure when the operating means has been switched tothe reverse setting.

As a result, the judgement for avoiding the stalling is made before thereverse setting to avoid a delay in control. Because the fittingpressure of the reverse driving clutch is set at the calculated initialfitting pressure as soon as the operating means is switched to thereverse setting, the stalling can be avoided and the effective reversedriving force as the braking force can be applied to the propeller toshorten time required for stopping the ship.

The criterion of judgement is a propeller speed when the clutchmechanism is switched from the forward setting to a neutral state by thecrash-go-astern operation to make the judgement for avoiding thestalling before the reverse setting.

Furthermore, calculation of the initial fitting pressure is performedbased on a setting map of the initial fitting pressure corresponding tothe propeller speed detected in the neutral state and the map is formedbased on a load characteristic intrinsic to a ship. In other words, byonly detecting the engine conditions such as the engine load and theengine speed, it is impossible to judge the drop amount of the enginespeed in fitting of the reverse driving clutch which is differentdepending on the characteristic of a ship load of each the ship and adeviation of the calculated initial fitting pressure from the actualproper value may be generated. In the invention, by forming the mapbased on the load characteristic intrinsic to the ship, the properinitial fitting pressure for each the ship can be set and the effectivecrash-go-astern operation can be achieved.

After the reverse setting, the initial fitting pressure is increased toa maximum value according to an increase in an engine speed. Asdescribed above, by automatically controlling to increase workinghydraulic pressure of the reverse driving clutch, it is possible to savetime and effort for a valve switching operation and to fit the reversedriving clutch in an optimum pressure increasing pattern to effectivelyapply the reverse driving force as the braking force to the propeller.

In order to cope with cases in which the load characteristic intrinsicto the ship cannot be specified or there is a deviation of an estimatedvalue from an actual value, the estimated load characteristic intrinsicto the ship is corrected according to a drop amount of an actual enginespeed when the reverse driving clutch is set at the initial fittingpressure and the map is corrected according to the corrected loadcharacteristic.

Moreover, the correction of the load characteristic intrinsic to theship is repeated until the drop amount of the actual engine speed whenthe reverse driving clutch is set at the initial fitting pressureconverges into a target range to thereby form a more accurate map toachieve the effective crash-go-astern operation. In this case, it isalso possible that the number of corrections of the load characteristicintrinsic to the ship is set in advance.

The load characteristic intrinsic to the ship may change due to secularchanges and the like of the ship. Therefore, the correction of the loadcharacteristic intrinsic to the ship is carried out again when the dropamount of the engine speed which has converged into the target range atone time deviates again from the target range.

Above and other objects, features, and effects of the invention willbecome apparent from the following descriptions based on theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an oil hydraulic circuit of a marine reduction and reversegear suitable for a crash-go-astern control according to the presentinvention.

FIG. 2 is a block diagram of a crash-go-astern control structureaccording to the invention.

FIG. 3 shows an engine speed and clutch hydraulic fluid over time duringa prior-art crash-go-astern operation.

FIG. 4 shows an engine speed and clutch hydraulic pressure over timeduring the crash-go-astern operation when detection of the engine speedis used.

FIG. 5 is a flow chart of a clutch hydraulic control in thecrash-go-astern operation based on detection of the engine speedaccording to the invention.

FIG. 6 shows a clutch lever signal value, an engine load, and the clutchhydraulic pressure over time during the crash-go-astern operation whendetection of the engine load is used.

FIG. 7 is a flow chart of the clutch hydraulic control in thecrash-go-astern operation based on detection of the engine loadaccording to the invention.

FIG. 8 shows the clutch lever signal value, a ship velocity, and theclutch hydraulic pressure over time during the crash-go-astern operationwhen detection of the engine speed and the ship velocity is used.

FIG. 9 shows the clutch hydraulic pressure over time when standby clutchpressure is varied up and down.

FIG. 10 is a flow chart of the clutch hydraulic pressure control in thecrash-go-astern operation based on detection of the engine speed and theship velocity according to the invention.

FIG. 11 shows the clutch lever signal value, the engine speed, and theship load (ship velocity) over time for explaining timing of judgementof the standby clutch pressure or initial fitting pressure for avoidingstalling.

FIG. 12 is a setting map of the initial fitting pressure correspondingto a propeller speed in neutral shifting in the crash-go-asternoperation formed based on a characteristic of the ship load.

FIG. 13 is a control block diagram for carrying out clutch hydraulicpressure control by setting the initial fitting pressure based on theship load.

FIG. 14 is a flow chart of a clutch pressure control in thecrash-go-astern operation for setting the initial fitting pressureaccording to a detected propeller speed by using a map based on the shipload before reverse setting to control reverse clutch pressure accordingto the invention.

FIG. 15 shows the engine speed and the reverse clutch pressure over timefrom neutral setting to reverse setting during the crash-go-asternoperation.

FIG. 16 shows the engine speed over time to show a drop amount of theengine speed.

FIG. 17 shows progression of the drop amount of the engine speed and theinitial fitting pressure after respective correcting operations forcausing the drop amount of the engine speed to converge into a targetrange.

FIG. 18 is a flow chart formed by adding a course of map correctionbased on correction of the ship load by reading the drop amount of theengine speed to a course of the control in FIG. 14.

BEST MODE FOR CARRYING OUT THE INVENTION

First an oil hydraulic circuit of a marine reduction and reverse gear 1(an outward appearance of which is shown in FIG. 2) shown in FIG. 1 willbe described. A forward driving clutch (forward clutch 10) and a reversedriving clutch (reverse clutch) 90 are disposed in parallel to form aclutch mechanism 100. Both the forward clutch 10 and the reverse clutch90 are clutches engaged when pressure oil is supplied to the clutches.By switching a position of a forward/reverse change-over valve 2 (anoutward appearance of which is shown in FIG. 2) by operating a clutchlever 2 a attached to the forward/reverse change-over valve 2 to switchwhere to supply the pressure oil, the clutch mechanism 100 can beswitched among three states, i.e., a forward set state in which theforward clutch 10 is engaged and the reverse clutch 90 is disengaged, areverse set state in which the reverse clutch 90 is engaged and theforward clutch 10 is disengaged, and a neutral state in which both theclutches 10 and 90 are not supplied with the pressure oil anddisengaged.

A common structure of the forward clutch 10 and the reverse clutch 90will be described in detail. Each the clutch is a wet multiple discclutch in which steel plates 12 and friction discs 13 are disposedalternately. By actuating a hydraulic piston 11 with pressure oilsupplied by the forward/reverse change-over valve 2, each the steelplate 12 is pressed against each the friction disc 13. If the pressureoil is drawn into the forward/reverse change-over valve 2, the hydraulicpiston 11 is returned to an initial position by biasing force and eachthe steel plate 12 is disengaged from each the friction disc 13. All thefriction discs 13 of each the clutch 10, 90 are connected to an innergear (pinion gear) 15 and the steel plates 12 are connected to an outergear 14 rotated by, engine power irrespective of engagement anddisengagement of the clutch. If the clutch is engaged, i.e., the steelplates 12 and the friction discs 13 are pressed against each other, theinner gear 15 in each the clutch rotates integrally with the outer gear14 to rotate a large gear 16 engaged with the inner gear 15. The largegear 16 is fixed to an out put shaft 17 of the marine reduction andreverse gear 1 and an output terminal of the output shaft 17 projectingoutside the marine reduction and reverse gear 1 and an input terminal ofa propeller shaft 6 having a propeller 7 are connected to each other asshown in FIG. 2. Thus, rotation of the large gear 16 is transferred tothe propeller 7. In other words, power of an engine 8 shown in FIG. 2 istransferred to the propeller 7 through the forward clutch 10 or thereverse clutch 90 of the clutch mechanism 100.

By adjusting pressing force (clutch hydraulic pressure) of the hydraulicpiston 11 in each of the forward clutch 10 and the reverse clutch 90,the friction discs 13 can be caused to slip on the steel plates 12 toobtain a half-clutch state. The clutch hydraulic pressure is controlledby an electronic trolling device 20 (which is surrounded by a two-dotchain line in FIG. 1 and an outward appearance of which is shown in FIG.2) having a direct-coupled solenoid valve 3, a solenoid proportionalvalve 4, and a low-speed valve 5. This structure will be described.

Discharged oil of an oil pump 22 is supplied to one of the forwardclutch 10 and the reverse clutch 90 through the low-speed valve 5 andthe forward/reverse change-over valve 2 forward or reverse setting ofthe clutch, i.e., the clutch lever 2 a of the forward/reversechange-over valve 2 is in a forward position or a reverse position. Atthis time, if the direct-coupled solenoid valve 3 is in a directcoupling set position as shown in FIG. 1, by using pressure oil sentfrom the direct-coupled solenoid valve 3 as pilot hydraulic pressure,pressure sent from the low-speed valve 5 corresponds to specified clutchhydraulic pressure, sufficient specified clutch hydraulic pressure isgenerated in the forward clutch 10 or the reverse clutch 90 suppliedwith pressure oil such that the steel plates 12 and the friction discs13 are pressed against each other without slipping and that thehydraulic piston 11 is fully pressed, and power from the outer gear 14is fully transferred to the inner gear 15.

If the direct-coupled solenoid valve 3 is in an opposite position to theposition shown in FIG. 1, pressure oil is introduced into the low-speedvalve 5 through the solenoid proportional valve 4. As this pressure oilfunctions as the pilot hydraulic pressure, a sent amount from thelow-speed valve 5 is adjusted by duty control of the solenoidproportional valve 4, the clutch hydraulic pressure of the forwardclutch 10 or the reverse clutch 90 supplied with the pressure oil isadjusted to be the specified pressure or lower, and a slippage of thefriction disc 13 on the steel plate 12 is adjusted. In other word, bythe switch of the direct-coupled solenoid valve 3 and adjustment of acurrent value of the solenoid proportional valve 4, fitting pressure ofthe forward clutch 10 or the reverse clutch 90 is adjusted.

Discharged oil of the oil pump 22 is supplied to the electronic trollingdevice 20 after hydraulic pressure of the discharged oil is adjustedthrough a clutch hydraulic pressure adjusting valve 24. Surplus pressureoil is supplied as lubricating oil to both the clutched 10 and 90 fromthe clutch hydraulic pressure adjusting valve 24 through an oil cooler26 and a lubricating oil pressure adjusting valve 27.

A position of the clutch hydraulic pressure adjusting valve 24 iscontrolled by hydraulic control of a loose-fitting valve 25 to adjustvalve-opening specified pressure of the valve 24. The loose-fittingvalve 25 is hydraulically connected to the forward/reverse change-overvalve 2 and returns to an initial position when the forward/reversechange-over valve 2 is in a neutral position to make the valve-openingspecified pressure of the clutch hydraulic pressure adjusting valve 24small in the neutral state. Immediately after the forward/reversechange-over valve 2 is switched to the forward position or the reverseposition, a part of the sent oil from the forward/reverse change-overvalve 2 is gradually sent to the loose-fitting valve 25 to graduallyincrease the valve-opening specified pressure of the forward/reversechange-over valve 2 and eventually increase the pressure tovalve-opening specified pressure in normal forward/reverse traveling. Asa result because the hydraulic pressure of the clutch 10 or 90 graduallyrises when a navigating mode is switched from the neutral state to aforward traveling setting or a reverse traveling setting, it is possibleto prevent abrupt starting. In a crash-go-astern operation, although themode goes through the neutral state when it is switched from the forwardtraveling setting to the reverse traveling setting, the loose-fittingvalve 25 does not return to the initial position in the neutral statebecause the neutral state is only instantaneous. Therefore, when themode is switched to the reverse traveling setting, the position of theloose-fitting valve 25 is not changed from the position in the forwardtraveling setting and the rise in the clutch hydraulic pressure of thereverse clutch 90 is not delayed.

In FIG. 1, a reference numeral 21 designates a strainer and a referencenumeral 23 designates a safety valve for returning the discharged oil ofthe oil pump 22 to the Strainer 21 in an emergency.

Next, a clutch control structure of the marine reduction and reversegear for achieving a crash-go-astern control according to the inventionwill be described by using FIG. 2.

An engine speed sensor 31 for detecting an actual speed of the engine 8is attached to the engine 8 and a rack position sensor 32 for detectinga position of a control rack of a governor attached to the engine 8 isattached to the engine 8. Furthermore, a black smoke sensor 33 fordetecting an amount of black smoke in exhaust is attached in an exhaustpipe of the engine 8.

A signal of an actual engine speed (EN) detected by the engine speedsensor 31, a signal of the rack position detected by the rack positionsensor 32, a signal indicating the amount of black smoke detected by theblack smoke sensor 33, and a load signal indicating a load applied tothe engine 8 and calculated based on the these sensors and the like areinput into an engine condition analyzing circuit 41. Threshold values ofthe respective signals are set in the engine condition analyzing circuit41 and a detection signal is transmitted from the engine conditionanalyzing circuit 41 to a main controller 42 when each the detectionsignal value exceeds the threshold value. As this transmitting means,data communications such as a radio communication are employed, forexample.

The main controller 42 carries out various controls based on thedetection signals with regard to various conditions of the engine andsent from the engine condition analyzing circuit 41. As one of thecontrols, the main controller 42 transmits a control signal based on thedetection signals from the engine condition analyzing circuit 41 to atrolling controller 43.

Into the trolling controller 43, besides the signals from the maincontroller 42, a set propeller speed signal S5 indicating a set value ofa propeller speed by a trolling dial 9, a detection signal (clutch leverposition signal) LS of a position of the clutch lever 2 a of theforward/reverse change-over valve 2 by a clutch signal sensor 34, and anoutput speed (propeller speed PN) signal detected by a propeller speedsensor 35 attached to the output shaft 17 are input. From the trollingcontroller 43, ON/OFF signals (the trolling OFF signal refers to asignal for setting the direct-coupled solenoid valve 3 in theabove-described direct coupling set position and the trolling ON signalrefers to a signal for setting the direct-coupled solenoid valve 3 inthe opposite position to the direct coupling set position to achieveadjustment of the clutch hydraulic pressure by the solenoid proportionalvalve 4) of trolling is output to the direct-coupled solenoid valve 3and a duty value for determining a valve opening degree of the solenoidproportional valve 4 is output to the valve 4.

The crash-go-astern control of the invention is for getting out of theneutral state of the clutch mechanism 100 swiftly without stalling toachieve reverse traveling by determining the clutch hydraulic pressureof the reverse clutch 90 which can be set variously by thedirect-coupled solenoid valve 3 and the solenoid proportional valve 4 asdescribed above based on various conditions when the clutch lever 2 a isswitched to the reverse position.

First the crash-go-astern controls according to prior art and theinvention based on detection of the engine speed when the clutchmechanism 100 is switched to the reverse set state (when the clutchlever 2 a is switched to the reverse position R) will be described byusing FIGS. 3 to 5.

As shown in FIG.3 and the like, the clutch lever position signal valueLS is switched with the passage of time t from a signal value Findicating a state in which the clutch lever 2 a is in the forwardposition through a signal value N indicating a state in which the lever2 a is in the neutral position to a signal value R indicating a state inwhich the lever 2 a is in the reverse position by the crash-go-asternoperation.

Through such the crash-go-astern operation by the clutch lever 2 a,clutch hydraulic pressure Pf of the forward clutch 10 changes from amaximum value Pm in forward traveling to a minimum value (zero, for thesake of convenience) for maintaining the clutch neutral state in reversetraveling and then remains at Pf=0.

On the other hand, clutch hydraulic pressure Pr of the reverse clutch 90is a minimum value (zero, similarly for the sake of convenience) insettings of forward and neutral. When the clutch lever 2 a is switchedto the reverse position, the reverse clutch 90 is fitted at the maximumvalue Pm at one time. However, if conditions which may cause stalling(e.g., the engine speed lower than the threshold value, an overload ofthe engine, and an insufficient reduction in forward speed) aredetected, the clutch hydraulic pressure Pr is reduced to clutchhydraulic pressure (standby clutch hydraulic pressure) Pw for standby.

Conventionally, as shown in FIG. 3, the clutch hydraulic pressure Pr ofthe reverse clutch 90 during standby is zero (i.e., neutral state). Inthis state, because external forces other than water drag do not act ona ship, braking force does not act sufficiently on the ship (propeller7) and it takes much time to stop a ship. Moreover, conventionally, amanual operation of returning the clutch lever 2 a to the neutralposition N every time to make the clutch hydraulic-pressure Pr zero andswitching the clutch lever 2 a to the reverse position R if the enginespeed increases to some degree or the engine load reduces to some degreeis required and such an operation is complicated. Although a criterionof judgement of if the clutch hydraulic pressure Pr is reduced to thestandby value is the actual engine speed EN in a case shown in FIG. 3,the same is true when the engine load is used as the criterion.

In the invention, on the other hand, by setting the standby clutchpressure Pw at a value higher than zero in a range in which stalling canbe avoided as shown in FIG. 4 and the like, braking performance isenhanced because slight reverse driving force is applied to thepropeller 7 during standby for avoiding the stalling and, as a result,time required to stop the ship can be shortened.

FIG. 4 shows progressions of the engine speed and the clutch pressurewhen the control of the clutch hydraulic pressure Pr in thecrash-go-astern operation is carried out based on detection of theengine speed and FIG. 5 is a flowchart of the control. In theabove-described engine condition analyzing circuit 41, a map of a setvalue of the standby clutch hydraulic pressure Pw at the time of thereverse clutch pressure Pr based on the detected engine speed EN isstored. The detected value of the engine speed sensor 31 is input intothe engine condition analyzing circuit 41. If the detected value EN islower than the threshold value ENs, setting the clutch hydraulicpressure Pr at the standby clutch pressure Pw and the set value of thestandby clutch pressure Pw are transmitted to the main controller 42based on the map, based on which the switching signal of thedirect-coupled solenoid valve 3 and the duty value of the solenoidproportional valve 4 are output from the main controller 42 through thetrolling controller 43.

A course of the hydraulic control shown in FIG. 5 will be described byreference to a graph in FIG. 4. In the engine condition detectingcircuit 41, while the clutch lever 2 a is in the forward position (step101), i.e., while the forward clutch 10 is fitted, the threshold valueENs of the engine speed for avoiding stalling is determined based on theset engine speed. If the clutch lever 2 a which has been in the forwardposition F is switched to the reverse position R in the crash-go-asternoperation (step 102), the clutch hydraulic pressure Pr is increasedtoward the maximum value Pm to engage the reverse clutch 90 (step 103).If the actual engine speed EN (detected by the engine speed sensor 31)which has reduced due to the clutch engagement does not reach thethreshold value ENs for avoiding stalling (step 104), the reverse clutchhydraulic pressure Pr is raised to the maximum value Pm in this state.If the detected engine speed EN has reduced to the threshold value ENs(step 105), the engine condition detecting circuit 41 transmits a signalindicating this condition to the main controller 42. At the time, acontrol signal is transmitted from the main controller 42 through thetrolling controller 43 to the solenoid proportional valve 4 to reducethe clutch hydraulic pressure Pr to the standby clutch pressure Pw (step106) to wait an increase in the engine speed EN. Unless the engine speedEN increases to a reference value ENt, the reverse clutch hydraulicpressure Pr is maintained at the standby clutch pressure Pw (step 107).If the engine speed EN which has increased reaches the reference valueENs, the clutch hydraulic pressure Pr is raised again toward the maximumvalue Pm (step 108). If EN·ENs again because of the reduction in theengine speed EN due to the increase in the hydraulic pressure, thereverse clutch pressure Pr is reduced again to the standby clutchpressure Pw to wait an increase in the engine speed.

Not only the employment of the reference value ENt of the engine speedEN which has increased as described above but also employment of timercontrol can also be considered to raise the reverse clutch hydraulicpressure Pr from the standby clutch pressure Pw to the maximum value Pm.In other words, the reverse clutch hydraulic pressure Pr is maintainedat the standby clutch pressure Pw and increased to the maximum value Pmwhen proper amount of time has elapsed.

The standby clutch pressure Pw may be set at a constant value or may beset according to the engine speed EN detected by the engine speed sensor31. In other words, if the engine speed EN is high, the standby clutchpressure Pw is set at a slightly large value. Then, when the enginespeed EN has fully risen over ENs, standby time until the reverse clutch90 is formally fitted when the clutch hydraulic pressure Pr is themaximum value Pm is shortened and a shock in fitting of the clutch isavoided. If the engine speed EN is low, the standby clutch pressure Pwis set at a slightly small value. During standby, the load applied tothe engine from the reverse clutch 90 side is minimized to avoid afurther reduction in the engine speed to prevent stalling.

In increasing the reverse clutch pressure Pr which has been reduced tothe standby clutch pressure Pw at one time, it is possible to graduallyincrease the reverse clutch pressure Pr according to the value of theincreasing engine speed EN. In this manner, an optimum pressureincreasing pattern is obtained automatically without manually switchingthe valve. In this case, by using a correlation map between theabove-described engine speed EN and standby clutch pressure Pw, a valueof the standby clutch pressure Pw corresponding to the increasing enginespeed EN can be used as the reverse clutch pressure Pr.

It is also possible that the criterion of judgement of the standbyclutch pressure Pw is the engine load EL detected by the rack positionsensor 32 and the black smoke sensor 33 instead of the engine speed EN.In other words, in the above-described engine condition analyzingcircuit 41, a load threshold value Els (over which, the engine isoverloaded and there is a fear of stalling) and a set value of thestandby clutch pressure Pw corresponding to the signal value of theengine load detected by these sensors 32, 33, and the like are stored.In this case, the standby clutch pressure Pw may be set according to adegree of the engine load exceeding the load threshold value ELs. Thehigher the engine load, the smaller value the set value of the standbyclutch pressure Pw is set at to thereby reduce a percentage of the loadtransferred from the propeller 7 to the engine.

FIG. 6 shows progressions of the engine load and the clutch pressure inthe clutch hydraulic pressure control in the crash-go-astern operationbased on detection of the engine load and FIG. 7 is a flow chart of thecontrol. In the crash-go-astern operation, after the reverse clutch 90is fitted (steps 201 to 202), the reverse clutch pressure Pr is raisedto the maximum value Pm (step 203). If it is found that the engine loadEL has exceeded the load threshold value ELs and the engine has beenbrought into the overloaded state due to a shock of the fitting (step205), a command for reducing the clutch pressure Pr of the reverseclutch 90 to the standby clutch pressure Pw is output to the maincontroller 42, a switching signal of the direct-coupled solenoid valve 3and a duty value of the solenoid proportional valve 4 are output fromthe main controller 42 through the trolling controller 43, the clutchpressure Pr of the reverse clutch 90 is set at the standby clutchpressure Pw (step 206), and the standby clutch pressure Pw is maintaineduntil the detected engine load EL reduces to a certain reference valueELt (step 207). If the detected engine load EL reduces below thereference value ELt the reverse clutch pressure Pr is raised to themaximum value Pm (step 208). If the engine load EL increasing again dueto the raising of the hydraulic pressure does not exceed the loadthreshold value ELs, the reverse clutch 90 is fitted at the maximumvalue Pm of the reverse clutch pressure Pr (step 203). The reverseclutch pressure Pr is reduced again to the standby clutch pressure Pw ifthe engine load EL exceeds the load threshold value ELs (step 205). Thereverse clutch pressure Pr is increased to the maximum value Pm if theengine load EL does not exceed the load threshold value ELs (step 204).It is also possible to control a length of time that the standby clutchpressure Pw is maintained by a timer to increase the reverse clutchpressure Pr from the standby clutch pressure Pw to the maximum value Pmwithout using the engine load reference value ELt.

In the control of the reverse clutch pressure Pr based on the engineload, it is also possible to gradually increase the reverse clutchpressure Pr according to the reducing value of the engine load EL inincreasing the reverse clutch pressure Pr which has been reduced to thestandby clutch pressure Pw at one time to the maximum value Pm. In thismanner, an optimum pressure increasing pattern is obtained automaticallywithout manually switching the valve. When the standby clutch pressurePw is changed according to the engine load EL as described above, byusing a correlation map between the engine load EL and the standbyclutch pressure Pw, a value of the standby clutch pressure Pwcorresponding to the increasing engine load EL can be used as thereverse clutch pressure Pr.

FIG. 8 shows a progression of the clutch hydraulic pressure in thecrash-go-astern operation based on a correlation value between theengine speed EN and a ship velocity V. The higher a forward ship.velocity Vf at a start of execution of the crash-go-astern operation,the larger the load applied to the propeller 7 in switching the clutchfrom forward to reverse is. However, even if the forward ship velocityVf is high, a possibility of stalling is reduced if the engine speed ENis large. Conversely, if the ship velocity has been sufficientlyreduced, the threshold value ENs of the engine speed EN can be reducedand a possibility that the reverse clutch pressure Pr does not need tobe reduced to the standby clutch pressure Pw in the reverse setting ofthe clutch, i.e., that the reverse clutch can be fitted at the maximumvalue Pm is increased.

In the engine condition analyzing circuit 41, a function map forobtaining the threshold value ENs of the engine speed EN is stored as afactor of the ship velocity V (forward ship velocity Vf). Based on thefunction map, it is judged whether the reverse clutch pressure Pr is tobe increased to the maximum value Pm or reduced to the standby clutchpressure Pw in the reverse setting. It is also possible to store a mapfor setting the optimum standby clutch pressure Pw according to each thethreshold value ENs.

Moreover, in the control shown in FIG. 8, control for maintaining thestandby clutch pressure Pw until the ship velocity V (forward shipvelocity Vf) becomes zero is carried out in reverse setting of theclutch. In other words, the above-described control for increasing thereverse clutch pressure Pr to the maximum value Pm after maintaining thereverse clutch pressure Pr at the standby clutch pressure Pw for acertain time period is not carried out. However, because the reverseclutch pressure Pr stays at the Bow standby clutch pressure Pw duringthe reverse setting, it is impossible to apply braking force due toeffective reverse driving force to the propeller 7. Therefore, as shownin FIG. 9, it is possible to consider varying the reverse clutchpressure Pr up and down in a wave shape from the standby clutch pressurePw. Thus, it is possible to apply the braking force to the propeller 7in stages.

Such up-and-down variations of the clutch pressure in the wave shape canbe applied to the hydraulic control shown in FIGS. 4 and 5 and thehydraulic control shown in FIGS. 6 and 7.

Furthermore, in the present control, a control for increasing thereverse clutch pressure Pr from the standby clutch pressure Pw to themaximum value Pm is carried out at the time of the ship velocity V=0.Because the propeller 7 which has been rotating forward stops at thetime of V=0, by raising the reverse clutch pressure Pr to the maximumvalue Pm, the reverse driving force is effectively applied to thepropeller 7 and the ship stops and then can move on to the reversetraveling without a shock (i.e., the reverse velocity Vr increases).

By reference to FIG. 8, a course of a clutch hydraulic control shown inFIG. 10 will be described. In the controller 50, a setting map of thestandby clutch pressure Pw based on the engine speed EN and the forwardship velocity Vf is stored in advance as described above (step 301). Ifa shift from the crash-go-astern operation, i.e., a state of the clutchposition sensor value LS=F (step 302) to LS=R is found (step 303) bydetection of the position of the clutch lever 2 a, the engine speedthreshold value ENs is obtained and the standby clutch pressure Pw iscalculated by reading of the engine speed EN and the ship velocity V(forward ship velocity Vf) (step 304), based on which the fittingpressure Pr of the reverse clutch 90 is set at the standby clutchpressure Pw (step 305) and the ship velocity V becomes zero (step 306).After that, the fitting pressure Pr of the reverse clutch 90 isincreased to the maximum value Pm irrespective of the threshold valueENs (step 307).

As described above, by using the method of the invention, duringexecution of the crash-go-astern operation, because the reverse clutch90 is engaged constantly even with low fitting pressure after the clutchlever 2 a is once moved to the reverse position and a slight reversedriving force is applied to the propeller 7 even during standby foravoiding stalling, it is possible to gradually apply a load to thepropeller to brake while reducing a load applied to the engine tothereby shorten time required for stopping the ship.

The above three clutch control methods in the crash-go-astern are thecontrol methods in which, when clutch operating means (clutch lever 2 a)is moved the reverse set position, in process of increasing the reverseclutch pressure Pr to the maximum value Pmax at one time, the reverseclutch pressure Pr is reduced to the standby clutch pressure Pw foravoiding the stalling in some cases based on detection of various engineconditions. In other words, as shown in FIG. 11, timing of detection (ofthe engine speed, the engine load, and the like, for example) forcontrolling the reverse clutch pressure Pr is time t₂ when the clutchlever 2 a is switched from the neutral position to the reverse position.

In these control methods, however, detection of the engine conditionswhich are criteria of judgement of if the reverse clutch pressure Pr is,reduced to the standby clutch pressure Pw is late and the control may bedelayed.

On the other hand, in a control method described as follows, before thecrash-go-astern operation, initial fitting pressure of the reverseclutch pressure Pr is set in advance based on certain criteria ofjudgement at the time during forward traveling and the reverse clutchpressure Pr is first set at the initial fitting pressure when the clutchoperating means is switched to the reverse set position. In other words,time t₁ when the clutch lever detected value LS shifts from a forwardvalue F to a neutral value N in FIG. 11 is employed as detection timingof the criteria of judgement for controlling the reverse clutch pressurePr. As a result, as soon as the clutch lever 2 a is switched to thereverse position, the reverse clutch pressure Pr becomes the initialfitting pressure Po calculated based on the detection.

In the present control method, as a criterion of prediction andjudgement of the initial fitting pressure of the reverse clutch pressurePr, a load applied to the ship due to water drag, driving of the engine,and the like at a certain vehicle velocity, i.e., a load characteristic(ship load) SL intrinsic to the ship is used. If the vehicle velocity isV and a constant intrinsic to the ship is K, the ship load SL isobtained as SL=V*K, i.e., a value proportional to the ship velocity V.The constant K intrinsic to the ship is obtained by considering a shapeof the propeller, a shape and weight of the ship, engine torque, and thelike which are characteristics of the ship. If the ship load SL isobtained, it is possible to roughly predict a drop in the engine speedEN when the reverse clutch 90 is fitted from the neutral state.

In other words, when the ship is navigated at a certain engine speed ENand a certain propeller speed PN in traveling ahead, what determines adrop amount of the engine speed EN in fitting of the reverse clutch 90by the crash-go-astern operation is the ship load SL.

The ship load SL is proportional to the ship velocity V (Vf) asdescribed above and the ship velocity V is affected by the propellerspeed PN. Therefore, in the crash-go-astern operation, if the propellerspeed PN at the time of neutral between the forward setting and thereverse setting is obtained, the ship load SL from the neutral state tofitting of the reverse clutch can be obtained proportionally and thedrop amount of the engine speed EN can be predicted based on the shipload SL. It is possible to obtain the initial fitting pressure Po of thereverse clutch pressure Pr such that the engine speed EN which reducesde to the clutch fitting does not reduce to a stalling danger region.

Therefore, in the clutch mechanism 100, if the propeller speed PN in theneutral state is detected when the mechanism 100 shifts from the fitstate of the forward clutch 10 to the neutral state, it is possible tocalculate the optimum initial fitting pressure Po of the reverse clutchpressure Pr according to the propeller speed PN.

A correlation map between the propeller speed PN in the neutral state inthe crash-go-astern operation and the initial fitting pressure Po of thereverse clutch pressure Pr as shown in FIG. 12 is formed for each shipaccording to a characteristic of the ship load SL intrinsic to the shipand stored in a controlling controller 50 of the clutch mechanism 100shown in FIG. 13.

The initial fitting pressure Po is set such that the engine speed ENwhich reduces due to initial fitting of the reverse clutch 90 does notreduce to the stalling danger region. The higher the propeller speed PN,the larger the drop amount of the engine speed EN is. Therefore, theinitial fitting pressure Po is set at the small value such that a loadapplied from the propeller side to the engine side due to the initialfitting of the reverse clutch 90 is reduced. When the propeller speed PNis extremely low, the initial fitting pressure Po is set at the maximumvalue Pm of the reverse clutch Pr. The smaller the propeller speed PN,the more the ship velocity Vf has reduced. Therefore, it is unnecessaryto apply large reverse driving force which functions as the propellerbraking force and, as a result, the initial fitting pressure Po can bereduced.

FIG. 13 shows a schematic block diagram for carrying out the presenthydraulic pressure control. In this case, into the clutch controllingcontroller 50, detection signals are input from the engine speed sensor31 attached to the engine 8, the clutch lever position sensor 34attached to the reduction and reverse gear 1, and the propeller speedsensor 35 attached to the propeller shaft 6 are input. The controller 50sends output signals to the direct-coupled solenoid valve 3 and thesolenoid proportional valve 4 of the reduction and reverse gear 1 tocontrol the forward clutch pressure Pf and the reverse clutch pressurePr.

FIG. 15 shows a relationship between the engine speed EN and the reverseclutch pressure Pr until the clutch mechanism 1 is switched from theneutral state to the reverse driving state in the crash-go-asternoperation. First, an assumption that the reverse clutch pressure Pr atthe time of neutral is substantially zero as described above is made. Asdescribed above, at the time of neutral, the initial fitting pressure Poof the reverse clutch 90 corresponding to the propeller speed PN whichis a detected value from the propeller speed sensor 34 is determinedbased on the map shown in FIG. 13. Based on the initial fitting pressurePo, output control signals are transmitted from the controller 50 to thedirect-coupled solenoid valve 3 and the solenoid proportional valve 4 toraise the reverse clutch 90 to the initial fitting pressure Po by thetime the clutch lever 2 a is shifted from the neutral position N to thereverse position R.

When the clutch lever 2 a is switched to the reverse setting R, theengine speed EN reduces due to the initial fitting of the reverse clutch90 and then increases. The higher the engine speed EN, the more reversedriving force which acts as the braking force on the propeller 7 can beapplied without a fear of stalling. Therefore, by increasing the reverseclutch pressure Pr as the engine speed EN increases, the more brakingforce is added to the propeller 7 to shorten the time required forstopping the ship.

A course of the above series of control will be described by using aflow chart in FIG. 14. In the controller 50, the map of the initialfitting pressure Po of the reverse clutch pressure Pr corresponding tothe propeller speed PN based on the characteristic of the ship load SLis stored in advance as described above (step 401). When the clutchlever position sensor value LS changes from the forward value F to theneutral value N (steps 402 to 403), the propeller speed PN at that timeis obtained and the initial fitting pressure Po of the reverse clutchpressure Pr is obtained by using the map (step 404). Then, by the timethe clutch lever position sensor value Ls changes from the neutral valueN to the reverse value R, the reverse clutch pressure Pr (by this time,Pr=0) is increased to the initial fitting pressure Po (step 405). As aresult, at the time when the clutch lever 2 a is set in the reverseposition R (step 406), the reverse clutch 90 is at the initial fittingpressure Po which has been set swiftly. Although the engine speed ENreduces at one time due to the fitting pressure, because the reverseclutch pressure Pr is the initial fitting pressure Po calculated inadvance by using the map based on the ship load SL the engine speed ENreduces in a range without a fear of stalling without delay in control.

Then, the engine speed EN increases. At this time, the reverse clutchpressure Pr is increased according to the increase in the engine speed(step 407) and raised to the maximum value Pm, the reverse clutch 90 isfitted smoothly, and the reverse driving force is effectively applied tothe propeller 7 to brake.

FIG. 15 shows the engine speed EN and the reverse clutch pressure Prover time through the neutral state and the reverse set state of theclutch mechanism 100 in the crash go astern operation. The reverseclutch pressure Pr has been raised to the initial fitting pressure Po bythe time the clutch lever detected value LS is switched from the neutralvalue N to the reverse value R and stays at the initial fitting pressurePo for a while after the switch to the reverse value R. During thisperiod, the engine speed EN reduces as soon as the clutch lever 2 a isswitched to the reverse position R and the reverse clutch 90 is fittedat the initial fitting pressure Po. However, the reverse driving forceapplied to the propeller 7 through the reverse clutch 90 fitted at theinitial fitting pressure Po does not apply such a load as to causestalling to the engine 8. Therefore, the engine speed EN increases soon.Because the reverse clutch pressure Pr is increased to follow theincrease pattern, the reverse driving force as the braking force iseffectively applied to the propeller 7.

It is difficult to obtain the characteristic of the ship load asdescribed above in some cases. In other words, the constant K cannot beobtained in the above-described SL=V*K in some cases. The estimated shipload SL may deviate from an actual value in some cases. In order to copewith such cases, it is possible that the map of the initial fittingpressure Po corresponding to the propeller speed PN based on theestimated characteristic of the ship load is corrected according to thedrop amount ΔEN of the engine seed EN when the clutch mechanism 100 isswitched to the reverse setting.

As shown in FIG. 16, if the clutch mechanism 100 is switched from theneutral state to the reverse driving state (i.e., if the clutch lever 2a is switched from the neutral position N to the reverse position R),the engine speed EN drops. However, the drop amount ΔEN changesaccording to the degree of the ship load SL. Therefore, the ship load SLis corrected based on the drop amount ΔEN. The map of the initialfitting pressure Po corresponding to the propeller speed PN is correctedbased on the corrected ship load SL and, as a result, the initialfitting pressure Po can be corrected to be a proper value.

The corrected initial fitting pressure Po calculated based on thecorrected ship load SL is obtained as follows, for example.

Po=(ΔEN ₁ −ΔEN ₀)*Po ₁ *a

, where ΔEN₁ is the actual drop amount of the engine speed, ΔEN₀ is thedrop amount of the engine speed EN used for estimating the ship load SLbefore correction, Poi is the initial fitting pressure Po detected byusing the ship load SL before correction, and a is a gain constant.

By correcting the estimate of the ship load SL and calculating theinitial fitting pressure Po based on the corrected value as describedabove, it is possible to immediately correct the estimated initialfitting pressure Po₁ to the proper Po to fit the reverse clutch 90 so asto effectively apply the braking force while avoiding the stalling evenif the reverse clutch pressure Pr set at the initial fitting pressure Pois higher or lower than the proper pressure because of a deviation ofthe estimated drop amount of the engine speed from the actual amount.

The correction of the ship load SL by reading the drop amount ΔEN of theengine speed may be repeated until the drop amount converges into acertain target range. In other words, the drop amount ΔEN of the enginespeed EN reduces as the initial fitting pressure Po of the reverseclutch 90 reduces and increases as the initial fitting pressure Poincreases because the higher the initial fitting pressure Po, the higherload is applied to the engine due to the clutch fitting. Therefore, asshown in FIG. 17, such a drop amount of the engine speed that theinitial fitting pressure Po of the reverse clutch 90 becomes the propervalue is set in advance as a certain target drop amount range ΔENr. Theabove correction of the ship load SL is repeated such that the dropamount ΔEN of the engine speed converges into the target drop range ΔENrand eventually changes the set map of the initial fitting pressurecorresponding to the propeller speed shown in FIG. 12 to adjust theinitial fitting pressure Po to a proper value.

For example, the drop amount ΔEN of the engine speed can converge intothe target range ΔENr by reducing the initial fitting pressure Po in thenext correction if the drop amount ΔEN of the engine speed is largerthan an upper limit of the target range ΔENr and by increasing theinitial fitting pressure Po in the next correction if the drop amountΔEN of the engine speed is smaller than a lower limit of the targetrange ΔENr as shown in FIG. 17. In FIG. 17, a horizontal axis nindicates the number of corrections.

By repeating the ship load SL to adjust the initial fitting pressure Posuch that the drop amount ΔEN of the engine speed converges into theproper range ΔENr, it is possible to reliably avoid the stalling andefficiently and abruptly stop in the crash-go-astern operation.

If the number of corrections of the ship load SL until the drop amountΔEN in the engine speed converges into the proper range ΔENr issubstantially constant, the number n of corrections may be set inadvance.

If the drop amount ΔEN of the engine speed deviates again from thetarget range ΔENr because the ship load SL changes due to secularchanges and the like of the ship and the propeller 7 after the dropamount ΔEN of the engine speed converges into the range ΔENr at onetime, the ship load SL is corrected again to adjust the initial fittingpressure Po such that the drop amount ΔEN of the engine speed convergesinto the range ΔENr.

A flow chart in FIG. 18 is formed by adding a correcting step (step 408)of the initial fitting pressure Po by correction of the map by readingthe drop amount ΔEN to the flow Chart in FIG. 14 and the correction isrepeated (steps 409 and 410) until the engine speed drop amount ΔENconverges into the target range ΔENr.

POSSIBILITY OF INDUSTRIAL APPLICATION

As described above, the invention provides an effective hydraulic clutchcontrol method in the crash-go-astern operation of the ship mounted withthe marine reduction and reverse gear having the hydraulic forwardclutch and reverse clutch.

What is claimed is:
 1. A hydraulic clutch control method of a marinereduction and reverse gear in a crash-go-astern operation, for switchingoperating means of a hydraulic clutch mechanism provided to the marinereduction and reverse gear from a forward setting to a reverse settingin a stroke so as to abruptly stop a ship traveling forward, said methodcomprising the steps of: (i) when switching the operation means from theforward setting to the reverse setting, changing a clutch pressure froma forward driving clutch pressure to a reverse driving clutch pressurevia a neutral pressure; (ii) if it is judged that there is a fear ofstalling due to a shock of the clutch switching in the operation,dropping and maintaining the reverse driving clutch pressure at apredetermined standby clutch pressure set between the neutral pressureand a maximum pressure of the reverse driving clutch pressure andsuitable for avoiding stalling; (iii) if it is judged that there is nofear of said stalling, increasing the reverse driving clutch pressure;and (iv) repeating steps (ii) and (iii) until the crash-go-asternoperation becomes stable.
 2. The hydraulic clutch control method of amarine reduction and reverse gear in a crash-go-astern operationaccording to claim 1, wherein a threshold value of an engine speed isset as a criterion of judgement of a state in which there is fear ofsaid stalling and a detected engine speed and the threshold value arecompared with each other.
 3. The hydraulic clutch control method of amarine reduction and reverse gear in a crash-go-astern operationaccording to claim 1, wherein a threshold value of a load applied to anengine is set as a criterion of judgement of a state in which there issaid fear of said stalling and a detected degree of a load applied tosaid engine and said threshold value are compared with each other. 4.The hydraulic clutch control method of a marine reduction and reversegear in a crash-go-astern operation according to claim 1, wherein anengine speed and a ship velocity are detected as a criteria of judgementof a state in which there is said fear of said stalling.
 5. Thehydraulic clutch control method of a marine reduction and reverse gearin a crash-go-astern operation according to claim 1, wherein the fittingpressure of the reverse driving clutch is first increased to the maximumvalue as a target when the operating means of said hydraulic clutchmechanism is switched to the reverse setting in said crash-go-asternoperation and the fitting pressure is reduced to said standby clutchpressure if it is judged that there is the fear of the stalling in aprocess of increasing of the fitting pressure.
 6. The hydraulic clutchcontrol method of a marine reduction and reverse gear in acrash-go-astern operation according to claim 5, wherein a thresholdvalue of an engine speed is set as a criterion of judgement of a statein which there is fear of said stalling and a detected engine speed andthe threshold value are compared with each other.
 7. The hydraulicclutch control method of a marine reduction and reverse gear in acrash-go-astern operation according to claim 5, wherein a thresholdvalue of a load applied to an engine is set as a criterion of judgementof a state in which there is said fear of said stalling and a detecteddegree of a load applied to said engine and said threshold value arecompared with each other.
 8. The hydraulic clutch control method of amarine reduction and reverse gear in a crash-go-astern operationaccording to claim 5, wherein an engine speed and a ship velocity aredetected as a criteria of judgement of a state in which there is saidfear of said stalling.
 9. The hydraulic clutch control method of amarine reduction and reverse gear in a crash-go-astern operationaccording to claim 1, wherein said standby clutch pressure until saidengine gets out of a state in which there is said fear of said stallingwhen said operating means of said clutch mechanism has been switched tothe reverse setting is increased and reduced repeatedly at or below themaximum value of the clutch fitting pressure as an upper limit.
 10. Thehydraulic clutch control method of a marine reduction and reverse gearin a crash-go-astern operation according to claim 1, wherein increase inthe fitting pressure of the reverse driving clutch based on a judgementof a state in which there is no fear of stalling is carried outaccording to an increase in the engine speed.
 11. The hydraulic clutchcontrol method of marine reduction and reverse gear in a crash-go-asternoperation according to claim 1, wherein increase in the fitting pressureof the reverse driving clutch based on a judgment of a state in whichthere is no fear of said stalling is carried out according to areduction in an engine load.
 12. A hydraulic clutch control method of amarine reduction and reverse gear in a crash-go-astern operation forswitching operating means of a hydraulic clutch mechanism provided tothe marine reduction and reverse gear from a forward setting to areverse setting in a stroke so as to abruptly stop traveling forward,said method comprising the steps of: calculating an initial fittingpressure of a reverse driving clutch from a criterion of judgement of aship in advance before the switching to said reverse setting; whenswitching the operation means from the forward setting to the reversesetting, changing a clutch pressure from a forward driving clutchpressure to the initial fitting pressure via a neutral pressure; andincreasing the fitting pressure of the reverse setting when thecrash-go-astern operation becomes stable.
 13. The hydraulic clutchcontrol method of a marine reduction and reverse gear in acrash-go-astern operation according to claim 12, wherein said initialfitting pressure is increased to a maximum value according to anincrease in the engine speed.
 14. The hydraulic clutch control method ofa marine reduction and reverse gear in a crash-go-astern operationaccording to claim 12, wherein said criterion of judgement is apropeller speed when the clutch mechanism is switched from the forwardsetting to a neutral state by said crash-go-astern operation.
 15. Thehydraulic clutch control method of marine reduction and reverse gear ina crash-go-astern operation according to claim 14, wherein calculationof said initial fitting pressure is performed based on a setting map ofsaid initial fitting pressure corresponding to the propeller speeddetected in the neutral state and the map is formed based upon a loadcharacteristic intrinsic to a ship.
 16. The hydraulic clutch controlmethod of a marine reduction and reverse gear in a crash-go-asternoperation according to claim 15, wherein said estimated loadcharacteristic intrinsic to ship is corrected according to a drop amountof an actual engine speed when the reverse driving clutch is set at theinitial fitting pressure and said map is corrected according to thecorrected load characteristic.
 17. The hydraulic clutch control methodof a marine reduction and reverse gear in a crash-go-astern operationaccording to claim 16, wherein said correction of the loadcharacteristic intrinsic to the ship is repeated until the drop amountof the actual engine speed when the reverse driving clutch is set at theinitial fitting pressure converges into a target range.
 18. Thehydraulic clutch control method of a marine reduction and reverse gearin a crash-go-astern operation according to claim 17, wherein the numberof corrections of said load characteristic intrinsic to the ship is setin advance.
 19. The hydraulic clutch control method of a marinereduction and reverse gear in a crash-go-astern operation according toclaim 17, wherein the correction of the load characteristic intrinsic tothe ship is carried out again when the drop amount of the engine speedwhich has converged into the target range at one time deviates againfrom the target range.